THE HONEY FUNGUS 151 
They were described by Jos. Schmitz, whose account with 
some additions was included by de Bary in the first edition 
of his Morphologie der Pilze (1866), and at that time several 
different fungi which grew as parasites on the rhizomorphs 
were regarded as their fructifications by various authors. 
It was not until 1874 that Hartig discovered that both 
forms of rhizomorphs are mycelial growths of the fungus 
Armillaria mellea, or as it was then called Agaricus melleus. 
Brefeld in 1877 obtained rhizomorphs in pure cultures 
grown from spores of the fungus, and thereby confirmed 
the association. The following account is derived chiefly 
from de Bary, Hartig, and Brefeld, who worked out the 
development and morphology of the rhizomorphs in great 
detail. 
It will be best to begin with the germination of the spores. 
These germinate in a nutrient solution in a few days, though 
germination does not take place in pure water. On a decoc- 
tion of plums they produce circular masses of white mycelium 
which grow slowly, reaching a diameter of little more than 
5 cm. in about eight days, and then stop. Next, closely- 
woven masses of hyphae appear near the centre, which are 
at first light in colour, but later dark brown. These dense 
clumps of mycelium resemble the sclerotia (hard mycelial 
growths which function as perennating organs) of many 
fungi, and we may follow Brefeld in regarding the rhizo- 
morphs as sclerotia which have developed growing points 
by which unlimited extension and branching are rendered 
possible. 
Of a number of such sclerotium-like bodies only one or 
two develop into rhizomorphs ; the rest cease to grow and 
become covered with white hyphae. The growing points only 
become operative on the lower side of the sclerotia, not on 
the upper side where they lie free of the culture substratum. 
Once growing points are formed the rhizomorphs quickly 
grow parallel to the bottom of the dish, and only cease to 
lengthen when the nutrient material is used up. By remov- 
ing them to a fresh decoction Brefeld obtained renewed 
growth and profuse adventitious branching, and by further 
